Platelets in human essential hypertension: in vitro hyperreactivity to thrombin.

Platelet reactivity of normotensive and essential hypertensive subjects was examined in vitro. We determined the release of [3H]-serotonin induced by thrombin from washed platelets in the presence of calcium (10(-3) mol/l) or with EGTA (calcium free medium). The release was significantly higher from platelets of hypertensive subjects when compared with those of normotensive subjects. This difference was only found in the presence of external calcium. The present data suggest an intrinsic functional hyperreactivity of platelets from essential hypertensive patients, which may be linked to an alteration in calcium (Ca2+) handling.